CODEWITHSUNDEEP
pythonfunctionrandompygame
user2950875
user2950875

Reputation: 89

Lightning Function Python

I am currently working on writing a function as part of a functions assignment. I am using python 2.7.5 and pygame. We are supposed to write a recursive function that draws lighting. I am currently having an error with my code but I do not know what it is. Here is my code:

from math import *
from pygame import *
from random import *

screen=display.set_mode((800,600))


def lightning(screen,x,y,size,ang):
    if size > 5:
        rang = radians(ang)
        x2 = x-size*cos(rang)
        y2 = y+size*sin(rang)
        draw.line(screen,(200,180,0),(x,y),(x2,y2))
        lightning(screen,x2,y2,size-randint(1,10),ang-randint(-20,10))
        lightning(screen,x2,y2,size-randint(1,10),ang+randint(-10,30))

lightning(screen,400,0,100,randint(60,100))
running=True
while running:
    for evt in event.get():
        if evt.type==QUIT:
            runnning=False
    screen.fill((0,0,0))
    lightning(screen,400,0,100,randint(60,100))
    time.wait(500)

    display.flip()
 quit()

Currently, when I try to add another line of lightning (the "lightning(...)") it does not display any error in the shell and also does not display anything in the pygame window. When I have only one line, the lightning functions properly. I would just like to know where my error is and reasons to why it is causing the error. Any help is appreciated. Thanks.

Upvotes: 0

Views: 899

Answers (1)

furas
furas

Reputation: 142651

For size=100 function ligthning() is call 800 000 to 3 500 000 times.

If you add another line of lightning it gives you even 7 000 000 calls.

Maybe You don't see result because it works too long. Try your code for smaller size.

My code to count ligthning() calls.

from math import *
from pygame import *
from random import *

#---------------------------------------------------------------------

def lightning(screen, x, y, size, ang, count):
    if size > 5:
        rang = radians(ang)
        x2 = x-size*cos(rang)
        y2 = y+size*sin(rang)
        draw.line(screen,(200,180,0),(x,y),(x2,y2))
        count = lightning(screen,x2,y2,size-randint(1,10),ang-randint(-20,10), count)
        count = lightning(screen,x2,y2,size-randint(1,10),ang+randint(-10,30), count)
    return count + 1

#---------------------------------------------------------------------

screen = display.set_mode((800,600))

#lightning(screen,400, 0, 100, randint(60,100))

running = True

while running:

    for evt in event.get():
        if evt.type == QUIT:
            running = False
        elif evt.type == KEYDOWN:
            if evt.key == K_ESCAPE:
                running = False

    screen.fill((0,0,0))
    print 'count: ', lightning(screen, 400, 0, 100, randint(60,100), 0)
    display.flip()

    #time.wait(500)

quit()

EDIT:

Theoretically radint(1,10) can always give 1 so you can always have lightning(...,size-1, ...) and for size=100it can give 2**95 calls.

2**95 = 39 614 081 257 132 168 796 771 975 168L

Upvotes: 1

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